Even the most steel-hearted republican must feel some sympathy for Sophie Rhys-Jones, the "Countess of Wessex". Not for the first time, she has embarrassed herself royally. Yesterday she returned to Britain to face a full-dress carpeting from Buckingham Palace, doubtless delivered by the silky personage of the Queen's private secretary, Sir Robin Janvrin. Her crime was to have opened her heart to a make-believe Arab sheikh who turned out to be a reporter for the News of the World.

Sympathy is due because, once again, a newspaper has resorted to dodgy, intrusive means to pursue a story whose claim to be in the public interest is slim. Trickery and deception are tools which journalists can use in only the most exceptional circumstances - and exposing the private thoughts of a minor royal hardly count as those.

It is telling, however, that the NoW did not have to work hard to lure Ms Rhys-Jones into its trap. On the contrary, she was only too eager to meet their bogus sheikh, believing he would be a valuable client for her PR firm. And this gets us to the heart of the matter. For this latest episode illustrates the conflict of interest that exists between membership of a family obliged to stand outside politics, entirely free of taint, and commercial work as an image-maker for hire. Her firm cannot help but trade on her royal status: it is her proximity to the palace that her clients think they are buying. Her readiness to speak so freely about royal life to a potential client suggests the glimpse of majesty was a routine part of her pitch.

This conflict of interest should end. Trade secretary Stephen Byers is surely right that the confusion of "public and private" roles is untenable. Ms Rhys-Jones should wind up her firm immediately; her husband should do the same with Ardent, the TV company whose entire existence is parasitical on its royal provenance. It operates from a country estate provided by the Queen (which means us). He pays for it from the £141,000 pocket money given him each year by the Queen, which comes from the allocation we give to her. In other words, Ardent is a publicly subsidised company.

The Wessexes are right to want to work, but they cannot both be in private business and retain their royal status. They will have to choose. Once again we are seeing the anomalies that arise when a country tries to maintain an ancient, hereditary institution in a modern age.